Developing technologies in support of monitoring the health of astronauts and the operation of critical instrumentation are ongoing in order to develop a better understanding of the changes in the human body and equipment anticipated in future space exploration. Accordingly, the emergence of promising technologies such as nanotechnology has sparked efforts to develop operational electronic and sensing devices at the nanoscale level with performance and sensing resolutions not yet achieved. These efforts have resulted in great specificity attained by tailoring the surface of sensors (i.e., surface modification) by optical, chemical and physical means (i.e., via the creation of preferred end-groups using approaches such as self-assembled monolayers).
One key or unique issue with these approaches is that sensing takes place via the attachment of molecules of the desired species to the sensor end groups bringing it into an irreversible saturated state via physical adsorption or chemical adsorption. More importantly, in most instances, the nature of the sensor is such that its mean-time-before-failure (MTBF) is limited (e.g., sensors that are cantilever-based or any other rendition that contains moving parts). This poses a reliability concern especially when working with embedded sensors such as BioMEMS sensors, or sensors intended for remote, difficult to access locations such as spacecraft or robotic probes for planetary exploration.
Traditional approaches for developing state-of-the-art sensing technologies targeted for specific applications are costly, mostly due to the expensive laboratory and facilities infrastructure required for their fabrication and high-volume production. In addition, the hybrid integrated approach of the different circuit components makes size reduction difficult. Reduced size is a relevant requirement in applications such as Bio-embedded devices. Traditionally, even those sensing devices developed at the nanostructure level perform only a unifunctional, specific sensing task and not a dual switching/sensing function. Switching enables the device to autonomously respond to changes in normal conditions and trigger appropriate responses, and then revert to baseline operation once the environment being sensed has returned to normal.
For this dual functionality, the current state of the art on nano-switch/sensors are based on metal oxide components (e.g., ZnO) with circuits consisting of mechanical actuators such as cantilevers, which include many non-trivial fabrication steps. Furthermore, the mechanical nature of these conventional sensors limits reliability due to a reduction on the MTBF. This level of complexity may be a critical disadvantage that can hinder the transition of the device from laboratory demonstration to practical working applications.